Long answer: It depends on your emulator, your specific game ROM and your skills. If both bits of software support it and you know how to program a Pokemon into the emulator system, then yes you can. In addition, newer games have NPCs that you can trade with. Otherwise trading is a no-go.
Unfortunately you cannot trade Pokémon with other emulator users; However, you can trade yourself to port Pokémon between the two emulators.
No DS emulator has trade.
Just press the emulator’s option key (the key between the L and R keys) and select the link that is with the previous one. You can choose either this game or another game option. If you select another game, you will see a list of games in the folder. Select the one you want to trade with.
Have Pokémon Home and Sword or Shield on your Switch and a phone and connect them. Create a second Nintendo Account on your Switch that is connected to the internet. Add yourself as a friend and trade. This allows you to play through the entire game again and retrieve all the legends.
For the guides I found online showing how to trade with an emulator, they all involve simulating a WiFi connection and connecting to GTS. However, GTS has already been switched off for Generation IV. So this method doesn’t work anymore.
I heard that Wonder Trading requires a connection to Nintendo Online Services and unfortunately Citra doesn’t support that. You must instead use the emulated local wireless multiplayer feature, which means you can only trade with other Citra users who are also online.
As I understand it, fake games can’t stream Pokemon like this one. The cartridge is also recognized by my 3DS and DSi.
Connect to the GTS with Game 01. Deposit the Magikarp and ask for the Pokemon you want (you can make this as specific as you like), pay attention to the level and gender, we’ll need this later. Give yourself a message so that you can recognize yourself. Close game 01.
You can’t for the exact reasons you gave. While it would be possible if one of the in-game traders were willing to trade one, according to the Bulbapedia in-game trade list, there is no such trader.
PokeGen is a Windows utility that allows you to edit the save file of NDS Pokémon games. You can also generate action replay codes, modify the PokeDex, add wonder cards, edit items, and edit C-Gear skins.